President Donald Trump's administration will require citizens from 50 countries to post bonds of $15,000 to apply for U.S. entry visa, a State Department official said on Wednesday.

The official, speaking on condition of anonymity, said 12 countries are being added to a list that already includes 38 other nations, largely in Africa.

The expanded visa bond program, which requires those foreign nationals to pay $15,000 for a B1 or B2 visa for business and tourism, goes into effect on April 2, with aim being to prevent visitors from overstaying their visas, the official said.

The new nations included in the visa bond program are Cambodia, Ethiopia, Georgia, Grenada, Lesotho, Mauritius, Mongolia, Mozambique, Nicaragua, Papua New Guinea, Seychelles, and Tunisia.

The official said bonds will be returned to visa recipients who return home in compliance with the terms of the visa and the bond, or do not travel in the first place.

Since taking office last January, Trump, a Republican, has pursued a hard-line immigration policy, including an aggressive deportation drive, revocations of visas and green cards, and screens of social media posts and past speeches of immigrants.

Human rights groups have condemned Trump's immigration and travel-related policies, saying they curb due process guarantees and free speech. Trump and his allies say the policies seek to improve domestic security.

Last June, he issued a travel ban that fully or partially blocked citizens of 19 nations from entering the U.S. on national security grounds.

The State Department official said the visa bond program has reduced the number of people who overstay their visas.

The 38 nations previously included are Algeria, Angola, Antigua and Barbuda, Bangladesh, Benin, Bhutan, Botswana, Burundi, Cabo Verde, Central African Republic, Cote d’Ivoire, Cuba, Djibouti, Dominica, Fiji, Gabon, The Gambia, Guinea, Guinea-Bissau, Kyrgyzstan, Malawi, Mauritania, Namibia, Nepal, Nigeria, Sao Tome and Principe, Senegal, Tajikistan, Tanzania, Togo, Tonga, Turkmenistan, Tuvalu, Uganda, Vanuatu, Venezuela, Zambia, and Zimbabwe. (Reuters, but headline rejigged)